This invention relates to processing of tobacco to reduce alkaloid loss during drying. This invention further relates to a strong acid treatment of tobacco prior to drying.
In the manufacture of tobacco products, the moisture content of cured tobacco is raised to about 20-25% (wet basis) in order to cut the tobacco into shreds without unnecessarily breaking the tobacco into fine particles and dust. However, to further prepare this tobacco for use as a smoking article the cut tobacco is dried to a moisture content of about 14% or lower. During this drying step, alkaloid substances including nicotine are lost through vaporization and the alkaloid loss affects the final characteristics of the tobacco product.
References teaching various means of treatment of tobacco are known and include U.S. Pat. No. 2,914,072, Tyrer and Tyrer, which relates to the treating of poor quality tobacco with a solution of metal salts and a simple aliphatic acid. Certain acids including glycolic and latic are used. However, the reference includes the acidification with a process where the acids are applied to the tobaccos along primary and sometimes secondary catalysts. The primary catalysts include salts of cobalt, maganese, nickel, copper, chromium or silver while the secondary catalysts include salts of potassium, magnesium, barium and sodium. The references teach the use of acids only with the catalysts and the reference specifically states it was found that the catalyst is significantly more effective when the acid is added to the tobacco. The reference teaches addition of acid in the range of from 0% to 5% based on dry weight of the tobacco but generally approximately 1%.
U.S. Pat. No. 4,127,135, Comber, teaches a method of curing and processing tobacco by spraying or infecting the plant stalks or roots of growing plants to accelerate wilting and preventing the leaves from turning brown with various chemicals including phosphorous acid. Additionally, U.S. Pat. No. 2,224,833, Pfvetaer and Lasch, teaches spraying tobacco with solutions of 2% formic acid and solutions of 1.5 to 3.0% hydrochloric acid to prevent the formation of brown spots and then drying the tobacco.
No prior art reference is known which teaches the use of a strong acid, for example, phosphoric acid, to reduce alkaloid loss during tobacco drying; nor do any of the references teach acidification followed by drying where after drying the tobacco is treated with a chemically basic material.